The present invention generally relates to metal-oxide-semiconductor field-effect transistors (MOSFET), and more specifically, to MOSFET punch through stoppers.
The MOSFET is a transistor used for amplifying or switching electronic signals. The MOSFET has a source, a drain, and a metal oxide gate electrode. The metal gate is electrically insulated from the main semiconductor n-channel or p-channel by a thin layer of insulating material, for example, silicon dioxide or glass, which makes the input resistance of the MOSFET relatively high. The gate voltage controls whether the path from drain to source is an open circuit (“off”) or a resistive path (“on”).
N-type field effect transistors (NFET) and p-type field effect transistors (PFET) are two types of complementary MOSFETs. The NFET uses electrons as the current carriers and with n-doped source and drain junctions. The PFET uses holes as the current carriers and with p-doped source and drain junctions.
The FinFET is a type of MOSFET. The FinFET is a double-gate or multiple-gate MOSFET device that mitigates the effects of short channels and reduces drain-induced barrier lowering. The “fin” refers to the narrow channel between source and drain regions. A thin dielectric layer on either side of the fin separates the fin channel from the gate.
The drain current of MOSFETS may increase when a parasitic current path between the source and drain is present. Typically, the parasitic current path runs below the channel region of the device, and occurs when the source and drain regions of the MOSFET extend too close to each other proximate to the channel region. A punch through stopper is used to reduce or prevent the parasitic current. Typically, implanting dopants in the bulk substrate forms a punch through stopper that effectively reduces punch through.